package com.hmdp.utils;

import cn.hutool.core.lang.func.Func;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.RedisData;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.CACHE_SHOP_KEY;
import static com.hmdp.utils.RedisConstants.LOCK_SHOP_KEY;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }
    //封装缓存穿透
    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1.从Redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断是否命中空值
        if(json != null){
            //返回错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        if(r == null){
            //5.不存在，返回错误
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在，写入Redis
        this.set(key, r, time, unit);

        //7.返回
        return r;
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    //封装逻辑过期
    public <R, ID> R queryWithLogicExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1.从Redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(json)){
            //3.存在，直接返回
            return null;
        }
        //4.命中，json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断过期时间
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回店铺信息
            return r;
        }

        //5.2已过期，需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if(isLock){
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    R r1 = dbFallback.apply(id);
                    this.setWithLogicalExpire(key, r1, time, unit);
//                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException();
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }

        //6.4失败，返回过期商铺信息
        //7.返回
        return r;
    }
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        //直接返回有可能拆箱后空值
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
